The Diagnosis of Edema and Its Pathogenesis

Abstract

Edema is the presence of an excess of interstitial fluid and is an important sign of ill health in clinical medicine. It is most common within the peripheral subcutaneous space. The differential diagnosis of edema comprises four broad categories: elevated hydrostatic pressure, pathological sodium retention, reduced plasma oncotic pressure, inflammation, and intrinsic malfunction of the lymphatic circulation.

The presence of edema signals a failure of body fluid homeostasis.

• This homeostasis is governed by the Starling forces, namely, the hydrostatic and oncotic pressures that prevail in the plasma and in the interstitium, respectively.

• The modern view of the Starling forces suggests that there is a net, ever-diminishing filtration that occurs along the entire length of the capillary, with no venous reabsorption.

• Lymphatic homeostasis requires an equilibrium between the lymphatic load and the lymphatic transport capacity.